Biofuel Spills Could be More Dangerous than Oil

Researchers from the University of Michigan found that ethanol-based liquids mix actively with water, making a biofuel spill potentially more harmful to aquatic life than oil spills.

Nov 16, 2012

Ethanol, a component of biofuel made from plants such as corn, is blended with gas in many parts of the country, but has significantly different fluid properties than pure gasoline. A group of researchers from the University of Michigan discovered than ethanol-based fuels mix actively with water, which is much different from how pure gasoline interacts with water, and could be more dangerous to aquatic life.

“Ethanol/gasoline blends are often presented as more environmentally benign than pure gasoline, but there is, in fact, little scientific research into the effects these blends could have on the health of surface waters,” says Avery Demond, an associate professor and director of the Environmental and Water Resources Engineering program at the University of Michigan.

Previous reports written for the State of California include methods for calculating the spread of ethanol into water based on a passive diffusion/dispersion process, but the method was not based on strong scientific evidence of how the two fluids interact, so the Michigan researchers wanted to fill in some of the knowledge gaps.

They experimented by filling a tank with water, covering the water with a plate, and pouring ethanol mixtures on top. The plate was then pulled away and the researchers recorded videos of the two fluids as they began to mix. The videos showed flow patterns called convection cells forming at the interface of the ethanol mixture and water. The mixing of the two fluids produced heat that changed the density and viscosity of the fluid, giving rise to circulation currents. In contrast, pure gasoline is essentially insoluble in water and primarily remains on the surface where it vaporizes into the air.

As a next step, the researchers would like to study how different ethanol mixtures vaporize, helping them determine how much of a spill would end up mixed into the water and how much would volatilize into the air. Although ethanol is biodegradable, high concentrations can be toxic to fish and other aquatic life. The ethanol in ethanol/gasoline blends might also transport some of the carcinogenic components of gasoline into the water during the mixing process.

Ultimately, the research team hopes their work will help answer outstanding questions about how ethanol mixes with water, giving scientists and policy makers a firmer grasp of the potential risks of ethanol-based biofuels.